Generators having rotors that provide alternate magnetic circuits

ABSTRACT

A generator includes a stator that has permanent magnets that complete a magnetic circuit across a series of gaps and through a generator coil. The rotor also includes permanent magnets that complete a magnetic circuit across a gap and through a rotor coil. When the rotor poles align with the stator poles, the stator and rotor magnetic circuits are broken, and new magnetic circuits are completed between the stator and rotor permanent magnets that cross the gap between the stator and rotor poles. A rotor coil can be used to boost the attraction/repulsion between the rotor and stator magnets. Alternating between these magnetic circuits as the prime mover rotates the rotor generates electricity.

FIELD OF THE INVENTION

The field of the invention is electromagnetic generators that increaseefficiency using rotor field coils and rotor magnets to switch betweenalternate magnetic circuits.

BACKGROUND

The background description includes information that may be useful inunderstanding the present invention. It is not an admission that any ofthe information provided herein is prior art or relevant to thepresently claimed invention, or that any publication specifically orimplicitly referenced is prior art.

Alternating current generators in which the stators utilize permanentmagnets to provide the magnetic flux to armature coils suffer numerousdisadvantages. Maintaining terminal voltage when an external load isconnected to the generator, or when the external load varies, can betechnologically challenging. Additionally, much of the magnetic fluxfrom the permanent magnets is unused during operation of traditionalgenerators that utilize magnets.

To address these problems, U.S. Pat. No. 2,816,240 to Zimmermandiscloses a generator that includes field coils to maintain terminalvoltage. Zimmerman's stator comprises two sets of circular laminations,one of which has two permanent magnets inserted into two angularsegments removed from each lamination and oriented such that the likepoles face each other. A flux-reversing multi-pole rotor acts as a fluxreversing switch for the flux passing though the armature windings whensuccessive teeth of the rotor are in alignment with the successive polesof the stator. When an external load is connected to the generator,excitation of the field coils maintains terminal voltage. However,Zimmerman fails to efficiently use magnetic flux from the statorpermanent magnets, because Zimmerman's flux paths travel both throughthe rotor and around the stator circumference.

In U. S. Patent Application No. 2008/0272664, Flynn discloseselectromechanical devices that have increased power density andefficiency. Flynn's electromechanical devices have stators comprised ofalternating stator segments and permanent magnets. When Flynn's rotorshaft is rotated by external prime mover, Flynn's bridge and pole woundelectro-mechanical device functions as a generator with stator segmentshaving reluctance bridges with an air gap and a reluctance gap controlcoil. However, Flynn's electromechanical devices only decrease coggingtorque without providing any motive force.

Thus, there is still a need for generators that utilize alternatemagnetic paths to produce torque through the rotor and produceelectricity through the stator in an energy-efficient manner.

All publications identified herein are incorporated by reference to thesame extent as if each individual publication or patent application werespecifically and individually indicated to be incorporated by reference.Where a definition or use of a term in an incorporated reference isinconsistent or contrary to the definition of that term provided herein,the definition of that term provided herein applies and the definitionof that term in the reference does not apply.

SUMMARY OF THE INVENTION

The inventive subject matter provides a generator that produceselectricity using gaps in the stator and gaps between the stator androtor poles to alternate between magnetic circuits. One magnetic circuitconnects stator magnet pairs and travels through the stator, whichincludes gaps on either end of a generator coil wrapped around agenerator core. An alternate magnetic circuit connects stator and rotormagnets and crosses the gap between the rotor and stator poles as thepoles substantially align during operation of the generator.

Stators according to the inventive subject matter include first andsecond magnetic flux elements having first and second stator poles,respectively. A first magnetic flux donor, e.g., a permanent magnet,donates magnetic flux having a first polarity to the first magnetic fluxelement. A second magnetic flux donor, e.g., a permanent magnet, donatesmagnetic flux of having a second polarity, opposite to the firstpolarity, to the second magnetic flux element. The first magnetic fluxelement is magnetically coupled to the first end of the generator coreacross a first gap, and the second magnetic flux element is magneticallycoupled to the second end of the generator core across a second gap.Optionally, the stator can include a magnetic flux yoke, magneticallycoupled to the first and second ends of the generator core.

In an exemplary embodiment, a rotor comprises a third magnetic fluxelement having first and second rotor poles. A rotor coil wraps aroundthe third magnetic flux element. The third magnetic flux element alsoincludes a third gap that is at least partially disposed within therotor coil. Third and fourth magnetic flux donors donate magnetic fluxhaving the second and first polarities, respectively, to the thirdmagnetic flux element on opposite sides of the third gap and rotor coil.The third magnetic flux donor donates magnetic flux having the secondpolarity to the third magnetic flux element proximate to the first rotorpole, and the fourth magnetic flux donor donates magnetic flux havingthe first polarity to the third magnetic flux element proximate to thesecond rotor pole.

As the rotor rotates, alignment of the first rotor pole with the firststator pole creates a fourth gap having a reluctance that is less thanthe reluctance of the first gap. Because alignment of the first rotorpole with the first stator pole creates a lower reluctance path,magnetic flux from the first magnetic flux donor completes a magneticcircuit with magnetic flux from the third magnetic flux donor across thefourth gap. Passing current through the rotor coil as the first rotorand stator poles align augments the torque by adding magnetic flux tothe magnetic flux from the third magnetic flux donor.

The magnetic circuit between the first and third magnetic flux donorsbreaks as the first rotor pole rotates away from the first stator pole.Magnetic flux from the first magnetic flux donor passes through thefirst magnetic flux element, across the first gap, through the generatorcore and generator coil, across the second gap and through the secondmagnetic flux element to complete a magnetic circuit with the secondmagnetic flux donor. Thus, as the rotor rotates, magnetic flux throughthe generator coil varies, generating alternating current.

The stator may further include a magnetic flux yoke that magneticallycouples to the first and second ends of the generator core.

In another embodiment, the third and fourth magnetic flux donorscomprise a permanent magnet disposed within the third gap. The rotorcoil directs magnetic flux of the first polarity toward the first rotorpole and magnetic flux of the second polarity to the second rotor pole.

It should be appreciated that the stator and rotor can each comprise anodd number of pole pairs.

Various objects, features, aspects and advantages of the inventivesubject matter will become more apparent from the following detaileddescription of preferred embodiments, along with the accompanyingdrawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A is a cross sectional view of a stator.

FIG. 1B is a cross sectional view of a rotor.

FIG. 1C shows a generator viewed down the rotational axis.

FIG. 1D shows the magnetic circuit formed when the stator and rotorpoles are substantially aligned.

FIG. 2A is a cross sectional view of a generator that has anotherembodiment of a rotor and shows a first magnetic circuit.

FIG. 2B shows the generator of FIG. 2A and a second magnetic circuit.

DETAILED DESCRIPTION

The following discussion provides many example embodiments of theinventive subject matter. Although each embodiment represents a singlecombination of inventive elements, the inventive subject matter isconsidered to include all possible combinations of the disclosedelements. Thus if one embodiment comprises elements A, B, and C, and asecond embodiment comprises elements B and D, then the inventive subjectmatter is also considered to include other remaining combinations of A,B, C, or D, even if not explicitly disclosed.

The generators described herein efficiently generate alternating currentusing alternate magnetic circuits. FIG. 1A shows an exemplary embodimentof stator 100. Stator 100 includes first magnetic flux elements 110 and120, which have first and second stator poles 111 and 122, respectively.Magnetic flux donors 101 and 102 magnetically couple to magnetic fluxelements 110 and 120, respectively. First magnetic flux element 110magnetically couples to first end 141 of generator core 140 across gap10, and second magnetic flux element 120 magnetically couples to secondend 142 of generator core 140 across gap 20. Generator coil 145 wrapsaround generator core 140. As shown in FIG. 1A, magnetic flux donor 101completes a stator magnetic circuit with magnetic flux donor 102. Thestator magnetic circuit travels through first magnetic flux element 110,across gap 10, through generator core 140 and generator coil 145, acrossgap 20, and through magnetic flux element 120. The stator can optionallyinclude magnetic flux yoke 160.

FIG. 1B shows rotor 150. Rotor 150 includes third magnetic flux element130, which has gap 30 at least partially disposed within rotor coil 135.Third magnetic flux element 130 has first and second rotor poles 131 and132, respectively. Third magnetic flux donor 103 and fourth magneticflux donor 104 magnetically couple to third magnetic flux element 130.Magnetic flux from third magnetic flux donor 103 and fourth magneticflux donor 104 completes a rotor magnetic circuit through third magneticflux element 130 and across gap 30.

FIG. 1C shows a generator viewed down the rotational axis. Stator 100has six pairs of stator poles. Rotor 150 has four pairs of rotor poles.As rotor 150 turns, first rotor pole 131 substantially aligns with firststator pole 111, as shown along axis 170 of FIG. 1C and in FIG. 1D. Asused herein, the term “substantially aligned” means that gap 40 betweenfirst rotor pole 131 and first stator pole 111 has a lower reluctancethan gaps 10, 20, and 30, so the stator and rotor magnetic circuits arebroken. Thus, when first rotor pole 131 and first stator pole 111 aresubstantially aligned, magnetic flux donors 101 and 103 complete analternate magnetic circuit that passes through stator pole 111, gap 40,and rotor pole 131. Similarly, magnetic flux donor 102 completes analternate magnetic circuit with magnetic flux donor 104. The magneticflux through these circuits can be augmented by applying current throughrotor coil 135. It should be appreciated that the on and off timing ofcurrent through rotor coil 135 is configured to boost rotor momentum.

As the rotor continues to rotate, the reluctance across gap 40 betweenthe rotor and stator poles increases and the alternate magnetic circuitis broken, and the stator and rotor magnetic circuits are reformed.Along axis 180 (FIG. 1C), the rotor poles are approximately midwaybetween the two nearest stator poles.

Another exemplary embodiment of a rotor according to the inventivesubject matter is illustrated in FIG. 2A. Rotor 250 comprises thirdmagnetic flux element 230 having gap 30. Third magnetic flux donor 203and fourth magnetic flux donor 204 are disposed within gap 30. Rotorcoil 235 wraps around magnetic flux element 230, and gap 30 extends atleast partially into rotor coil 235 toward both rotor poles 231 and 232.

Stator 200 includes first magnetic flux elements 210 and 220, which havefirst and second stator poles 211 and 222, respectively. Magnetic fluxdonors 201 and 202 magnetically couple to magnetic flux elements 210 and220, respectively.

FIG. 2A also shows the magnetic circuit formed when rotor poles 231 and232 are substantially aligned with stator poles 211 and 222,respectively. As first rotor pole 231 rotates toward first stator pole211, current is applied to rotor coil 235, directing magnetic flux fromthird magnetic flux donor 203 to complete a magnetic circuit across gap40 with magnetic flux from first magnetic flux donor 201. The magneticflux from rotor coil 235 also directs magnetic flux from forth magneticflux donor 204 to complete a magnetic circuit with second magnetic fluxdonor 202 across gap 50. Magnetic flux from rotor coil 235 boosts theattractive force between the rotor and stator poles.

As rotor 250 continues rotating, rotor poles 231 and 232 rotate out ofsubstantial alignment with stator poles 211 and 222, respectively, andcurrent through rotor coil 235 is reversed. Reversing the currentthrough rotor coil 235 reverses the direction of the magnetic flux frommagnetic flux donors 203 and 204 as shown in FIG. 2B, and the statorpoles repel the rotor poles, boosting rotor momentum. First magneticflux element 210 magnetically couples to first end 241 of generator core240 across gap 10, and second magnetic flux element 220 magneticallycouples to second end 242 of generator core 240 across gap 20. Generatorcoil 245 wraps around generator core 240. The stator may optionallyinclude magnetic flux yoke 260 that magnetically couples to first andsecond ends (241 and 242) of the generator core.

One should appreciate that the disclosed techniques provide manyadvantageous technical effects including efficiently using permanentmagnets to generate electricity by providing an alternate magneticcircuit through the rotor.

As used in the description herein and throughout the claims that follow,the meaning of “a,” “an,” and “the” includes plural reference unless thecontext clearly dictates otherwise. Also, as used in the descriptionherein, the meaning of “in” includes “in” and “on” unless the contextclearly dictates otherwise.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember can be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. One ormore members of a group can be included in, or deleted from, a group forreasons of convenience and/or patentability.

As used herein, and unless the context dictates otherwise, the term“coupled to” is intended to include both direct coupling (in which twoelements that are coupled to each other contact each other) and indirectcoupling (in which at least one additional element is located betweenthe two elements). Therefore, the terms “coupled to” and “coupled with”are used synonymously.

It should be apparent to those skilled in the art that many moremodifications besides those already described are possible withoutdeparting from the inventive concepts herein. The inventive subjectmatter, therefore, is not to be restricted except in the spirit of theappended claims. Moreover, in interpreting both the specification andthe claims, all terms should be interpreted in the broadest possiblemanner consistent with the context. In particular, the terms “comprises”and “comprising” should be interpreted as referring to elements,components, or steps in a non-exclusive manner, indicating that thereferenced elements, components, or steps may be present, or utilized,or combined with other elements, components, or steps that are notexpressly referenced. Where the specification claims refers to at leastone of something selected from the group consisting of A, B, C . . . andN, the text should be interpreted as requiring only one element from thegroup, not A plus N, or B plus N, etc.

What is claimed is:
 1. A generator comprising: stator comprising: agenerator coil wrapped around a generator core; a first magnetic fluxelement having a first stator pole, wherein the first magnetic fluxelement is magnetically coupled to a first end of the generator coreacross a first gap having a first reluctance; a first magnetic fluxdonor that donates magnetic flux having a first polarity to the firstmagnetic flux element; a second magnetic flux element having a secondstator pole, wherein the second magnetic flux element is magneticallycoupled to a second end of the generator core across a second gap havinga second reluctance; and a second magnetic flux donor that donatesmagnetic flux having a second polarity, opposite to the first polarity,to the second magnetic flux element; and a rotor comprising: a thirdmagnetic flux element having first and second rotor poles; a rotor coilwrapped around the third magnetic flux element, wherein the thirdmagnetic flux element has a third gap that is at least partiallydisposed within the rotor coil; a third magnetic flux donor that donatesmagnetic flux having the second polarity to the third magnetic fluxelement; and a fourth magnetic flux donor that donates magnetic fluxhaving the first polarity to the third magnetic flux element, andwherein the generator has a fourth gap between the first stator pole andthe first rotor pole when the first rotor pole is substantially alignedwith the first stator pole, and wherein the first reluctance is greaterthan a reluctance of the fourth gap when the first rotor pole issubstantially aligned with the first stator pole.
 2. The generator ofclaim 1, wherein the first, second, third and fourth magnetic fluxdonors are permanent magnets.
 3. The generator of claim 1, wherein thethird magnetic flux donor comprises a permanent magnet magneticallycoupled to the third magnetic flux element on a same side of the rotorcoil as a third rotor pole.
 4. The generator of claim 3, wherein thefourth magnetic flux donor comprises a permanent magnet magneticallycoupled to the third magnetic flux element on a same side of the rotorcoil as a fourth rotor pole.
 5. The generator of claim 4, furthercomprising a magnetic flux yoke that completes a magnetic circuitbetween magnetic flux of the second polarity from the third magneticflux donor and magnetic flux of the first polarity from the fourthmagnetic flux donor.
 6. The generator of claim 1, wherein the third andfourth magnetic flux donors comprise a permanent magnet disposed withinthe third gap.
 7. The generator of claim 1, further comprising amagnetic flux yoke, magnetically coupled to the first and second ends ofthe generator core.
 8. The generator of claim 1, wherein the statorcomprises an odd number of pole pairs.
 9. The generator of claim 1,wherein the rotor comprises an odd number of pole pairs.